Source : Free On-Line Dictionary of Computing

ThingLab
     
        A {simulation} system written in {Smalltalk-80}.  It solves
        {constraint}s using {value inference}.
     
        Version: ThingLab II.
     
        ["The Programming Language Aspects of ThingLab, A
        Constraint-Oriented Simulation Laboratory", A. Borning, ACM
        TOPLAS 3(4):353-387 (Oct 1981)].